1. Field of the Invention
The present invention relates to an epoxy resin composition for encapsulating a semiconductor and a semiconductor device using the same.
2. Description of the Related Art
Electronic components such as diodes, transistors and integrated circuits have been typically encapsulated with an epoxy resin composition. Particularly, in integrated circuits, there have been used epoxy resin compositions exhibiting excellent heat resistance and moisture resistance containing an epoxy resin, a phenol resin, and inorganic fillers such as fused silica and crystalline silica. However, recent market trend to size reduction, weight saving and higher performance in electronic devices has led to more integrated semiconductors and accelerated surface mounting of a semiconductor device, while an epoxy resin composition used for encapsulating a semiconductor element has been required to meet increasingly stricter conditions. In particular, now that surface mounting of a semiconductor device is common, a moistened semiconductor device is exposed to a high temperature during a solder reflow process. Furthermore, as part of eliminating environment burden materials, a lead-free solder has been increasingly used as an alternative material, but has a higher melting point than that of a conventional solder. Therefore, it needs a reflow temperature during surface mounting higher by about 20° C. than a conventional case, specifically 260° C. Thus, a semiconductor device is exposed to a further higher temperature, causing delamination of a cured epoxy resin composition in its interface with a semiconductor element or lead frame. It tends to defects significantly deteriorating reliability in a semiconductor device such as cracks.
An epoxy resin composition frequently contains halogen-containing flame retardant such as bromine-containing organic compounds and an antimony compound such as diantimony trioxide and diantimony tetroxide for making it flame-resistant, but in the light of eliminating environment burden materials, there have been needs for developing an epoxy resin composition exhibiting excellent flame resistance without a halogen-containing flame retardant or antimony compound. As alternative environmentally-benign flame retardant, metal hydroxides such as aluminum hydroxide and magnesium hydroxide have been used. They must be, however, used in a large amount for serving as a flame retardant. When being used in an enough amount to obtain required flame retardant property, it may deteriorate fluidity of an epoxy resin composition during molding, mechanical strength of a curing or cured material and thus solder-reflow resistance.
To solve these problems, there have been proposed using a low water-absorbing, flexible and flame-resistant resin for improving solder reflow resistance (See, for example, Japanese Laid-open Publication No. 1-275618, Japanese Laid-open Publication No. 5-097965, and Japanese Laid-open Publication No. 5-097967). However, such technique cannot be practically used because increase in a content of an inorganic filler for using a lead-free solder causes inadequate fluidity.
Given such circumstances, there has been needed for developing a resin composition for encapsulating a semiconductor exhibiting higher flame resistance, good fluidity and adequately higher solder-reflow resistance to allow for the use of a lead-free solder without a flame retardant.
The present invention has been achieved for resolving the above problems. Thus, an object of the invention is to provide a resin composition for encapsulating a semiconductor exhibiting higher flame resistance, good fluidity and adequately higher solder-reflow resistance to allow for the use of a lead-free solder without a flame retardant, as well as a highly reliable semiconductor device in which a semiconductor element is encapsulated with such a composition.